increasing throttle response? flywheel or throttle body?

[JohnL]

...make sure the voltage's we are looking for are 0.48-0.49V closed throttle and 4.5V Wide Open Throttle ...

Checked mine (CB7 Accord).

WOT was 4.52v, closed throttle was only 0.44v. Now, the WOT number suggested that the TPS was correctly adjusted (i.e. TPS rotation relative to throttle plate), but that the throttle stop was probably slightly worn allowing the throttle plate to close slightly more than it's supposed to do (throttle stop contact being a probable wear point over an extended period of time).

To raise the closed throttle voltage (since it seemed probable that the TPS was already correctly positioned), rather than attempt to rotate the TPS relative to the throttle plate (which would bring the closed throttle into spec but at the expense of throwing off the WOT voltage), I adjusted the throttle stop slightly until the closed throttle number rose to 0.5v.

This was maybe half a turn or less on the adjuster. I'm not sure exactly because turning the adjuster screw was rather awkward, but it wasn't much. I now have; closed throttle = 0.5v and WOT = 4.52v. This opened the throtle plate a touch which raised the base idle by about 100rpm, which I readjusted by closing the idle speed screw slightly.

Since then I've only had the chance to drive the car with a load full of passengers (which isn't normal operating conditions for this car), so (being conscious of possible placebo effects) I'm not 100% sure but impressions so far are that low rpm / light throttle torque seems to be significantly improved (I'll know better after some driver only time).

This seems most noticable when taking off from rest, appearing to require less clutch slippage with the engine feeling more 'muscular' at low rpm / light throttle opening. There also seems to be some improvement to throttle response when 'blipping' for 'rev matching' on downshift.

[JohnL]

imo i dunoo a car with a heavy duty clutch+light flywheel feels like it has more off the line torque compared to stock.....

A lightweight flywheel wil make the engine feel as if it had less low rpm torque, which in effect it will because there will be less kinetic energy 'stored' in the inertial mass of the rotating flywheel.

If you imagine an extreme hypothetical example of a flywheel with zero mass, then when taking off from rest all the power required to get the car's mass into motion must come from the power that the engine is producing at the moment the clutch engages, which won't be enough unless the rpm is substantially raised (increasing energy 'stored' in the engines rotational masses such as cranshaft), and / or the throttle opened significantly wider (to make more instantaneous power), and / or the clutch is slipped substantially.

.......Like it just makes the car jump lol.
Stock clutches feel laggy

Because you're revving the engine higher and / or opening the throttle wider, and dumping the clutch harder. The extra torque is coming from the engine being somewhat higher in the rpm range (where torque is higher), wider throttle opening, and from the kinetic energy embodied in the faster spinning rotational mass being higher due to the higher rpm. It's not because of a lighter flywheel...

[JohnL]

Cheers John,your welcome mate!

Mate,you need to learn how to service your car,therefore have it runnin' in top condition all the time.You will be suprised how well your car will go.Here's a list,an old post I made:

Beeza,
My engine is already well maintained and runs very nicely. Checking the TPS is just one of those things I've been meaning to do but haven't yet gotten around to doing since the engine was running well with good economy. Your posting of the voltage specs prompted me to check mine since not knowing the spec was no longer a valid excuse to leave this on the back burner...

PS a small number of things on your list are open to debate...

[beeza]

Sorry John!

That was for the OP,dsee2,Oops!,I didn't make myself clear in the post...

Your knowledge of cars is incredible John,I wouldn't say something like that to you mate!

Tell me the things you speak of!

P.S. I soooo stoked I've 'helped' to give back to ya!!

[JohnL]

Your knowledge of cars is incredible John,I wouldn't say something like that to you mate!

I'm no automotive encyclopaedia, and there are 'real' experts out there, but I have learnt at least a few things over the years. I have large blind spots in my knowledge, mostly to do with all the electrickery in modern engine management systems.

Tell me the things you speak of!

It's only a few things, I agree with most of it. I'll get back to you, domesticity calls...

P.S. I soooo stoked I've 'helped' to give back to ya!!

Yes it has definitely helped, the engine is significantly more 'drivable' now. It's producing more part throttle torque so is more effortless / relaxing to drive in a sedatish manner (but of course there is no discernable difference at large throttle openings).

Less clutch slippage is now needed on take off and some hills that used to need a downshift or largish throttle opening can now be driven up on a light throttle with no downshift. Downshift 'blips' are definitely more consistent / predictable with noticably faster rpm rise.

I've been meaning to check this for ages, but since the engine was running acceptably I kept forgetting about it. I'm a bit surprised how much difference there is between 0.44v and 0.5v...

[SHU-ES1]

can I check my d17 tps the same way you guys have tested your d16s I'm assuming? Our tb's are vertical, and I think the d16 are horizontal? I'd like to do this but my car is only reaching 8 years old. Do you think it would improve my throttle response? I could do with not downshifting and light throttle while going up hill!!! Sounds like an awesome maintenance tip!!

[JohnL]

can I check my d17 tps the same way you guys have tested your d16s I'm assuming? Our tb's are vertical, and I think the d16 are horizontal?

The orientation of the TPS won't make any difference.

My car is an Accord (with an f22a9 engine). I did some checking online, and from what I've found it seems that all Honda TPSs use a potentiometer with the same output values, and so the WOT / closed throttle outputs should be 4.5v and 0.5v for all models.

I'd like to do this but my car is only reaching 8 years old. Do you think it would improve my throttle response?

Only if your TPS is giving the ECU a significantly incorrectly calibrated signal, you won't know unless you check it. I don't really know what constitutes the lower end of 'significant' in this case, but I can tell you that 0.06v below 0.5v is significant.

Note that with my car I didn't disassemble the TPS, clean it etc, only checked the voltage output at closed throttle and WOT. I wouldn't be removing / opening up the TPS just to clean it, only if I were already going to the trouble of removing the attachment bolts from the TB (in order to be able rotate the TPS).

Note that the TPS attachment fasteners are bolts, but ones that have no means by which they can be turned (such as a hex head, screwdriver slot etc). To remove them you need to cut a slot in the head in order to get a screwdriver to engage the bolts, I can't see why it's necessary to cut the head completely off one as beeza has done (but he may know something I don't...).

Don't assume that if the closed voltage output is below spec that the TPS actually needs to be adjusted (rotated). Over time the throttle stop contact point is bound to wear to some degree (or someone may have ignorantly fiddled with the stop adjustment at some point...), so in high mileage cars it's probably inevitable (?) that the closed throttle TPS voltage eventually falls somewhat below spec. This is not a TPS problem, it's a throttle stop problem...

With my car I found that the WOT voltage was almost pefect, but only the closed voltage was out of spec. In this case any adjustment to the TPS itself (to bring the closed voltage into spec) was going to throw the WOT setting off, so I made an adjustment to the throttle stop that only affected the closed voltage output (noting that the throttle plate should never actually be fully closed in the 'closed' position).

I could do with not downshifting and light throttle while going up hill!!! Sounds like an awesome maintenance tip!!

It's worked beyond expectations with my engine. The TPS output is at least worth checking (but you can't fix it if it ain't broke...).

[JohnL]

Beeza,
As promised, here’s my critique on some of your earlier points. Please prefix IMO to the front of my comments.

You wrote:
“Clean contact points in the dizzy and lightly sand the rotor on the outer edge where it sparks on the contact points”

The build up on the rotor arm tip and cap electrodes is a good conductor from which a spark propagates easily. Sanding it off increases the gap and does more harm than leaving the build up alone. Excessive build up and / or erosion should be addressed by replacing the rotor arm and dizzy cap.

“Change the oil and oil filter (every 5000km's)”

This isn’t a bad idea of course, but not really needed unless you are doing a lot of slow city driving and / or short trips that don’t allow the oil to remain at full operating temperature for reasonably long periods. If you do a lot of highway / open road driving, then 10,000 km oil changes should be fine. City driving is bad for oil, higher speed / longer distance runs is much less demanding.

Driving in dusty conditions is also a good reason to go to 5000km changes, as is driving involving a lot of hard acceleration.

“Change the fuel filter every 2nd oil change”

Not a bad idea, but overkill, especially as EFI filters aren’t all that cheap. Fuel filters don’t block up all that quickly unless you have an unfortunate encounter with particularly dirty fuel. Other than that I’d stick to Hondas recommended service interval (every 40,000km). If in doubt, do a fuel flow test before replacing the filter.

“Transmission oil is every 20,000km's”

Yes for auto transmission fluid.

For manual gearboxes it can’t hurt, but oil lasts a very long time when not exposed to and contaminated by combustion by-products. I’d put 100,000kms on this, especially if using a purpose formulated manual transmission oil (rather than engine oil).

“Use BP Ultimate 98 fuel only (1/2 a tank max at a time if your keen)”

Too sweeping a statement. Brands aside, and all else being equal, using a higher octane fuel than the engine actually requires doesn’t result in greater power output or better economy than using a lower octane fuel, so long as the engine can use the lower octane without detonation. If the engine runs fine on lower octane fuel then using a higher octane fuel will most probably result in a very slightly lower power output and worsened economy.

This is because the ****tail of chemicals used to increase the octane rating are added to the brew in substantial quantities, displacing a very significant % of the base ‘petrol’ content with substances that have a significantly lesser calorific value, i.e. there is less energy embodied in each CC of higher octane fuel than in each CC of lower octane fuel (i.e. lower octane petrol fuels have a higher calorific value per unit of volume than higher octane).

Note that an engine gains power output and improved economy as the CR is increased. As the CR is increased the need to use higher octane fuel increases, but this is only to avoid ‘detonation’ of the compressing air / fuel mixture. The power and economy increases comes from the higher CR, not from the higher octane fuel.

“Also look into advancing the timing 2-3 degrees”

I won’t say that this won’t improve power output because it well might, but I’d only try this if I were measuring the outcome on a dynamometer. Note that detonation / pre-ignition is usually audible as a ping or rattle, but not always...

“Insulate your fuel lines - prevent the fuel from getting warm/hot”

Any research data to back this up? There may be some potential benefit, but my bet is that at best it’s microscopically small...

[beeza]

Thank John!

Do you mind if I use a quote or 2 of your's in my DIY on the tps,just to show people how effective this mod is?

I had to cut the top of the rivets off because the tps needs to be screwed down,much easier to replace it with a screw then stuff around with the rivet.I couldn't see it working with the rivet.

[beeza]

Beeza,
As promised, here’s my critique on some of your earlier points. Please prefix IMO to the front of my comments.

You wrote:
“Clean contact points in the dizzy and lightly sand the rotor on the outer edge where it sparks on the contact points”

The build up on the rotor arm tip and cap electrodes is a good conductor from which a spark propagates easily. Sanding it off increases the gap and does more harm than leaving the build up alone. Excessive build up and / or erosion should be addressed by replacing the rotor arm and dizzy cap....

Gotcha

“Change the oil and oil filter (every 5000km's)”

This isn’t a bad idea of course, but not really needed unless you are doing a lot of slow city driving and / or short trips that don’t allow the oil to remain at full operating temperature for reasonably long periods. If you do a lot of highway / open road driving, then 10,000 km oil changes should be fine. City driving is bad for oil, higher speed / longer distance runs is much less demanding.

Driving in dusty conditions is also a good reason to go to 5000km changes, as is driving involving a lot of hard acceleration.

Yes I agree.5000 is a bit of overkill but your car will run better when the oil is changed.So $75 vs a lil better performance.Every car will be different here but certainly my car runs better.

“Change the fuel filter every 2nd oil change”

Not a bad idea, but overkill, especially as EFI filters aren’t all that cheap. Fuel filters don’t block up all that quickly unless you have an unfortunate encounter with particularly dirty fuel. Other than that I’d stick to Hondas recommended service interval (every 40,000km). If in doubt, do a fuel flow test before replacing the filter.

It certainly sounds like it! But I just changed mine,it would have been a bit more than 20k,maybe 30k... but it again made a significant difference! A noticeable difference.I was quite suprised.

“Transmission oil is every 20,000km's”

Yes for auto transmission fluid.

For manual gearboxes it can’t hurt, but oil lasts a very long time when not exposed to and contaminated by combustion by-products. I’d put 100,000kms on this, especially if using a purpose formulated manual transmission oil (rather than engine oil).

It's the same story as the engine oil.My car is an auto,so changing the fluid in mine makes a great difference.Not real sure about manual transmissions.

“Use BP Ultimate 98 fuel only (1/2 a tank max at a time if your keen)”

Too sweeping a statement. Brands aside, and all else being equal, using a higher octane fuel than the engine actually requires doesn’t result in greater power output or better economy than using a lower octane fuel, so long as the engine can use the lower octane without detonation. If the engine runs fine on lower octane fuel then using a higher octane fuel will most probably result in a very slightly lower power output and worsened economy.

This is because the ****tail of chemicals used to increase the octane rating are added to the brew in substantial quantities, displacing a very significant % of the base ‘petrol’ content with substances that have a significantly lesser calorific value, i.e. there is less energy embodied in each CC of higher octane fuel than in each CC of lower octane fuel (i.e. lower octane petrol fuels have a higher calorific value per unit of volume than higher octane).

Note that an engine gains power output and improved economy as the CR is increased. As the CR is increased the need to use higher octane fuel increases, but this is only to avoid ‘detonation’ of the compressing air / fuel mixture. The power and economy increases comes from the higher CR, not from the higher octane fuel.

Gotcha,Cheers! I will putting in 91 octane then! Or should I...I cant hear my car ping or anything but at 100km/h when cruising on the freeway is does little hesitates/surges/misfire (but not),it only does it on 91 octane fuel and only at 100-100km/h?

“Also look into advancing the timing 2-3 degrees”

I won’t say that this won’t improve power output because it well might, but I’d only try this if I were measuring the outcome on a dynamometer. Note that detonation / pre-ignition is usually audible as a ping or rattle, but not always...

Forsure forsure.Worth giving a shot though!

“Insulate your fuel lines - prevent the fuel from getting warm/hot”

Any research data to back this up? There may be some potential benefit, but my bet is that at best it’s microscopically small...

Probably but it all adds up! Logically it makes sense,a cooler fuel going into the mix will be more compressed and therefore produce more power.

It took me 10 minutes to insulate my fuel lines with air conditioning tape

[JohnL]

Do you mind if I use a quote or 2 of your's in my DIY on the tps,

No worries.

just to show people how effective this mod is?

Sorry to be pedantic, but it's not really a modification as such, it's returning the TPS to it's correct stock condition, so it's more like 'tuning'.

I think it would be better to say 'can be' rather than 'is', because the effectiveness will vary according to how far the calibration has driffted over time.

Out of curiosity, how far out were your voltages before you 'tuned' them? Also, when you rotated the TPS, did you move the WOT voltage off spec in order to achieve the correct closed throttle spec? If 'yes' then you might want to consider returning the WOT voltage to spec and resetting the closed throttle to spec using the throttle stop screw.

I had to cut the top of the rivets off because the tps needs to be screwed down,much easier to replace it with a screw then stuff around with the rivet.I couldn't see it working with the rivet.

While checking around to verify whether your quoted voltages applied to my Accord, I saw a couple of references to the stock TPS "rivets" actually being blind headed bolts threaded into the TB casting (so can't be undone with 'normal' tools, Honda obviously doesn't want anyone messing with the TPS setting). So if this is correct there should have been no need to grind the head off, just cut a screwdriver slot...

[JohnL]

Yes I agree.5000 is a bit of overkill but your car will run better when the oil is changed.So $75 vs a lil better performance.Every car will be different here but certainly my car runs better.

75$? You're using fully synthetic aren't you? A good synthetic should last longer than a good mineral based oil, so IMO you're really throwing money away. If you're going to change the oil every 5000km you might as well use a good mineral oil.

What you seem to be doing might be reasonable insurance for a very high performance / stressed / high $ build engine, but not otherwise, really.

It certainly sounds like it! But I just changed mine,it would have been a bit more than 20k,maybe 30k... but it again made a significant difference! A noticeable difference.I was quite suprised.

Then I'll bet you got a dose (or doses) of dirty fuel somewhere / sometime before the changeover. I've changed a fuel filter that had at least 100,000km on it, and seen no performance change, not that I really expected there to be one since the filter had passed a flow test with flying colours (I just felt I should change it 'just in case' and that it was so old).

Be careful of placebo affects too. I'll swear that my car goes harder and even handles better after I've cleaned it...

Gotcha,Cheers! I will putting in 91 octane then! Or should I...I cant hear my car ping or anything but at 100km/h when cruising on the freeway is does little hesitates/surges/misfire (but not),it only does it on 91 octane fuel and only at 100-100km/h?

Use 91 if that's the fuel specified by Honda for your engine (and you haven't increased the CR or supercharged it). Without being able to make any categorical statement, I suspect your problem above to be either coincidental with some other problem, and / or maybe you have had some bad 91 octane fuel.

You should always try to buy fuel from a high turnover outlet as fuel that's been sitting in the servo's tanks too long can go stale and lose octane rating along with some of the properties that make it ignite readily in the combustion chamber...

Forsure forsure.Worth giving a shot though!

Advancing the ignition timing on speculation is potentially dangerous because you may get what is in effect pre-ignition, which can cause damage (the dyno will tell you what's what...). If you do this I suspect the ECU may well 'retard' the timing back to stock in any case, unless you advance the base timing so far it's beyond the ECUs parameters to correct...

Probably but it all adds up! Logically it makes sense,a cooler fuel going into the mix will be more compressed and therefore produce more power.

Many things (very many, and not just to do with cars...) seem to be 'common sense' or "logical", but in reality are incorrect assumptions. Cooler fuel may be very slightly denser, so the mixture may be very slightly richer with a cooler fuel, which may or may not be a good thing. Cooler fuel may very slightly lower the temperature of the inducted air, cooling it ever so slightly more as the fuel is injected resulting in a very slightly greater quantity of air being inducted, but at best it will be a miniscule difference...

I tried this when karting, i.e. chilling the fuel in an esky and using an insulated tank and lines on the kart. Never made a jot of difference as far as I could tell, and didn't show up on the stop watch either...